diff --git a/src/loader/beacon_api.rs b/src/loader/beacon_api.rs
index 8054e2a..ae91703 100644
--- a/src/loader/beacon_api.rs
+++ b/src/loader/beacon_api.rs
@@ -457,7 +457,7 @@ extern "C" fn beacon_format_append(format: *mut Formatp, text: *const c_char, le
 
 /// Append a formatted string to this object.
 #[no_mangle]
-unsafe extern "C" fn beacon_format_printf(format: *mut Formatp, fmt: *const c_char, args: ...) {
+unsafe extern "C" fn beacon_format_printf(format: *mut Formatp, fmt: *const c_char, mut args: ...) {
     if format.is_null() {
         return;
     }
@@ -603,7 +603,7 @@ pub extern "C" fn beacon_get_output_data() -> &'static mut Carrier {
 
 /// Format and present output to the Beacon operator.
 #[no_mangle]
-unsafe extern "C" fn beacon_printf(_type: c_int, fmt: *mut c_char, args: ...) {
+unsafe extern "C" fn beacon_printf(_type: c_int, fmt: *mut c_char, mut args: ...) {
     // Use a buffer large enough for most format operations
     let mut buffer = vec![0u8; 4096];